Cyclic stress-controlled tests on offshore clay

One of the main concerns in cyclic behavior of soft clay is gradual degradation with the progression of loading cycle. A series of cyclic constant-volume direct simple shear (CDSS) loading tests was performed on Malaysia offshore clay to study its undrained degradation. The testing program consists of stress-controlled tests with cyclic shear ratio ranging from 0.34 to 0.83 at different overconsolidation ratios (OCRs). For a given cyclic stress ratio in stress-controlled tests, the accumulated cyclic strain and pore water pressure increase with elevated number of cycles. In heavily overconsolidated clay specimens, the negative cyclic pore water pressure is generated followed by positive cyclic pore water pressure as cyclic tests progress. The post-cyclic strength of offshore clay specimens is reduced by undrained cyclic stress-controlled loading.